CN109988644B

CN109988644B - Method for producing gasoline and low-freezing-point oil by catalyst grading technology

Info

Publication number: CN109988644B
Application number: CN201711470702.6A
Authority: CN
Inventors: 王仲义; 崔哲; 彭冲; 曹正凯; 孙士可; 吴子明
Original assignee: China Petroleum and Chemical Corp; Sinopec Dalian Research Institute of Petroleum and Petrochemicals
Current assignee: Sinopec Dalian Petrochemical Research Institute Co ltd; China Petroleum and Chemical Corp
Priority date: 2017-12-29
Filing date: 2017-12-29
Publication date: 2021-02-05
Anticipated expiration: 2037-12-29
Also published as: CN109988644A

Abstract

The invention discloses a method for producing gasoline and low freezing point diesel oil by using a catalyst grading technology. The method comprises the following steps: a) mixing the heavy oil raw material with hydrogen, and then performing limited hydrofining reaction in a reaction zone containing a hydrofining catalyst bed; b) under the condition of a hydro-conversion process, enabling the reaction effluent obtained in the step a) to pass through a reaction zone containing a graded wax oil hydro-conversion catalyst bed layer, and enabling the reaction effluent to enter a flash tank for separation to obtain a gas phase and a liquid phase; c) carrying out subsequent separation, steam stripping and fractionation on the gas phase obtained in the step b) to obtain converted gasoline; d) and c) carrying out hydrocracking/isomerization reaction on the liquid phase in the step b) through a reaction zone containing a wax oil hydrocracking catalyst bed under a hydrocracking condition, and separating and fractionating reaction effluent to obtain heavy naphtha, low-freezing-point diesel oil and unconverted oil. The method can obtain high-quality gasoline blending components and low-freezing point diesel oil, and has good economic benefit.

Description

Method for producing gasoline and low-freezing-point oil by catalyst grading technology

Technical Field

The invention relates to a method for treating wax oil components, in particular to a method for producing high-quality gasoline and by-product liquid phase products such as high-quality low-freezing-point oil by processing wax oil raw materials through a catalyst grading technology.

Background

Gasoline is one of the most used light petroleum products, is an important fuel of an engine, can be obtained by different units for petroleum refining, and in the process of crude oil processing, units such as distillation, catalytic cracking, thermal cracking, hydrocracking, catalytic reforming and the like all produce gasoline components, but have different octane numbers, such as the octane number of straight-run gasoline is low, and the gasoline cannot be independently used as engine fuel; in addition, the sulfur content of impurities is different, so that the gasoline component with high sulfur content also needs to be desulfurized and refined, and finally, the gasoline component is blended, and if necessary, a high-octane component needs to be added, so that the gasoline product meeting the national standard is finally obtained.

At present, the main ways for producing gasoline in China are catalytic cracking and catalytic reforming. The catalytic cracking is the most important secondary processing process in the petroleum refining industry at present, and is also the core process for the heavy oil lightening, along with the increasing heavy oil of the world, the processing capacity of an FCC device is continuously improved, various heavy oils are used as raw materials, the main product, namely the high-octane gasoline, is obtained through catalytic cracking reaction, but because the emission standard of the gasoline at present is improved, the production of the catalytic cracking gasoline requires the pre-refining of the raw materials and the post-refining of the product; the catalytic reforming is a process for rearranging the molecular structure of hydrocarbons in gasoline fractions into a new molecular structure, is an important means for improving the quality of gasoline and producing petrochemical raw materials, is an essential process for producing gasoline at present, and has high requirements on the source and cleanliness of the raw materials due to the reaction process and the characteristic requirements of catalysts.

The hydrocracking technology has the advantages of strong raw material adaptability, flexible product scheme, high liquid product yield, good product quality and the like, and is favored by oil refining enterprises of various countries in the world for many years. Hydrocracking, which is one of the main processes for deep processing of heavy oil, can also indirectly produce gasoline components, and due to the characteristics of the processes, the produced heavy naphtha has extremely low impurity content and low octane number, which is exactly opposite to that of catalytic gasoline, and the heavy naphtha is used as a feed of a catalytic reforming unit to produce high-octane gasoline after molecular structure rearrangement. In addition, the hydrocracking technology can also produce high-quality low-freezing point oil products through the adjustment of the catalyst and the process technology, and the diesel oil component can be taken as a low-freezing point diesel oil product to leave a factory, and particularly has obvious market benefit in northern high latitude areas or high cold areas; the tail oil component can also be used as a base oil raw material of the lubricating oil, and the lubricating oil is not limited by the regulation and control of macroscopic economic price in principle due to the particularity of production mode and market demand, is one of high-quality products creating income and increasing efficiency of various large oil refining enterprises, and is favored and valued by the enterprises.

CN104611029A discloses a catalytic cracking diesel oil hydro-conversion method, wherein catalytic diesel oil and hydrogen gas are mixed and then enter a hydrofining reactor for hydrofining reaction, and then enter a hydrocracking reactor for hydrocracking reaction. Although gasoline with high octane number is produced through a hydro-conversion process, catalytic cracking diesel oil is still used as a raw material essentially, and the range of the raw material for producing high-quality gasoline is not expanded, so that the method has certain limitation.

CN101724454A introduces a hydrocracking method for producing high-octane gasoline, raw oil and hydrogen are mixed and then enter a reactor to be sequentially subjected to hydrofining and hydrocracking reactions, although the method has the characteristics of capability of processing more inferior raw materials, long operation period of a catalyst, good quality of a hydrocracking product and the like. But the used raw material is still the diesel oil component, and heavy oil is not used for directly producing high-octane gasoline.

CN103184073A introduces a hydrocracking method for producing high-octane gasoline blending components, wherein raw oil is subjected to controlled hydrofining and hydro-conversion reaction, although the target product can be high-octane gasoline or blending components through process control, the selection range of the raw material is single, the production cannot be carried out by utilizing heavy oil products, and meanwhile, the catalyst is not effectively improved aiming at the process.

Disclosure of Invention

Aiming at the problems in the prior art, the technical problem to be solved by the invention is to provide a hydrocracking process method for processing heavy raw materials to produce high-octane gasoline and high-quality low-pour-point oil. The method carries out restrictive hydrogenation saturation on a conventional heavy raw material, then carries out a hydro-conversion reaction, produces high-quality gasoline or blending components under the conditions of certain process condition limitation and special catalyst grading, simultaneously separates reaction products, carries out cracking reaction on non-gasoline liquid phase components, can also produce low-freezing point oil products, is used as fuel oil products or lubricating oil base oil and the like, and furthest produces target products on the basis of realizing selective processing on heavy fractions.

The invention provides a method for producing gasoline and low freezing point diesel oil by a catalyst grading technology, which comprises the following steps:

a) under the condition of hydrofining, the heavy oil raw material and hydrogen are mixed and then pass through a reaction zone containing a hydrofining catalyst bed layer to carry out limited hydrofining reaction;

b) carrying out a limiting hydroconversion reaction on the reaction effluent obtained in the step a) through a reaction zone containing a graded wax oil hydroconversion catalyst bed under the hydroconversion process condition, separating the reaction effluent in a flash tank, obtaining a gas phase containing a gasoline component at the upper part, and obtaining a liquid phase with the distillation range larger than that of the gasoline fraction at the lower part;

c) carrying out subsequent hydrogen separation, steam stripping and fractionation on the gas phase obtained in the step b) to obtain converted gasoline;

d) and c) carrying out hydrocracking/isomerization reaction on the liquid phase in the step b) through a reaction zone containing a wax oil hydrocracking catalyst bed under the hydrocracking process condition, and carrying out gas-liquid separation, fractionation and other processes on the obtained reaction effluent to obtain target products such as heavy naphtha, low-freezing diesel oil, unconverted oil and the like.

The final boiling point of the heavy oil raw material in the step a) is generally 450-580 ℃, preferably 480-570 ℃, and the density is generally 0.92g/cm³Above, preferably 0.93g/cm³Above, the total aromatic hydrocarbon in the raw material is above 40wt%, preferably above 45wt%, and the nitrogen content is 800mg g^-1Above, preferably 1000mg g^-1The above. Typically one or more of vacuum wax oil, deasphalted oil or coker wax oil, and can be selected from the above-mentioned components obtained by processing middle east crude oil or Liaohe crude oil, and the other impurity property of raw material is defined by its technical abilityThe knowledge of the common sense of the domain must be such that it meets the requirements that can be used as a feed for a hydrocracking unit.

The hydrofining process conditions in the step a) are as follows: the reaction pressure is 6.0-13.0 MPa, the volume ratio of hydrogen to oil is 200: 1-3000: 1, and the volume airspeed is 0.1-5.0 h^-1The reaction temperature is 260-435 ℃; the preferable operation conditions are that the reaction pressure is 7.0-12.0 MPa, the volume ratio of hydrogen to oil is 300: 1-900: 1, and the volume airspeed is 1.0-3.0 h^-1The reaction temperature is 300-430 ℃.

The limiting hydrofining reaction in the step a) is to control a certain hydrogenation saturation depth to avoid the influence of the over saturation of the aromatic hydrocarbon component in the heavy oil raw material on the octane number of a gasoline fraction product, and the nitrogen content of the refined oil (namely the reaction effluent obtained in the step a) is generally required to be controlled to be 50-250 mg g.g.^-1Preferably 100 to 200 mg/g^-1Thus, the nitrogen content of the refined oil can be reduced while the aromatic hydrocarbon component in the raw material can be retained to the maximum extent. It should be noted that, in the course of the hydrorefining reaction, by controlling the nitrogen content of the refined oil, the aromatic hydrocarbon component in the reaction effluent has a low content of tricyclic and higher aromatic hydrocarbon components, and the total content is generally 1 to 20wt%, preferably 2 to 15 wt%.

The hydroconversion process conditions in the step b) are as follows: the reaction pressure is 6.0-13.0 MPa, the volume ratio of hydrogen to oil is 300: 1-1200: 1, and the volume airspeed is 0.1-5.0 h^-1The reaction temperature is 280-455 ℃; the preferable operation conditions are that the reaction pressure is 7.0-12.0 MPa, the volume ratio of hydrogen to oil is 400: 1-1000: 1, and the volume airspeed is 1.0-3.0 h^-1The reaction temperature is 310-440 ℃.

The limiting hydroconversion reaction in the step b) is to control a certain hydroconversion depth, so that the octane number of a gasoline fraction product is prevented from being influenced by excessive cracking of non-aromatic hydrocarbon components in the reaction effluent in the step a), and the yield of high-quality gasoline fraction in the total product is generally required to be controlled to be 10-40 wt% according to the difference of the raw materials and the aromatic hydrocarbon in the reaction effluent in the step a), so that the aromatic hydrocarbon components in the raw materials can be retained to the maximum extent and converted into the gasoline fraction while the heavy oil raw materials are processed, and the octane number of the gasoline product is improved.

The flash separation in the step b) can select an independent separation tank, and can also use the thermal high fraction in the thermal high fraction process as a gasoline flash separation tank, preferably the latter, the process conditions are that the reaction pressure is 6.0-13.0 MPa, is slightly lower than the pressure in the hydroconversion process, the temperature is 150-300 ℃, the thermal high fraction is generally controlled according to the conventional knowledge in the field according to the yield of the converted gasoline and the product quality, and the main purpose is to separate the crude gasoline fraction in the reaction process.

The hydrocracking process conditions in the step d) are as follows: the reaction pressure is 6.0-13.0 MPa, the volume ratio of hydrogen to oil is 300: 1-1200: 1, and the volume airspeed is 0.1-5.0 h^-1The reaction temperature is 280-455 ℃; the preferable operation conditions are that the reaction pressure is 7.0-12.0 MPa, the volume ratio of hydrogen to oil is 400: 1-1000: 1, and the volume airspeed is 1.0-4.0 h^-1The reaction temperature is 310-440 ℃.

The hydrocracking/isomerization reaction in the step d) is characterized in that the hydrocracking/isomerization depth of the material flow entering the section is controlled according to the product requirement, proper heat exchange or material flow heating is carried out before the material flow enters according to the reaction temperature requirement, and the mode of separating the crude gasoline from the front section is adopted, so that the non-aromatic components in the reaction feed material do not need to be controlled deliberately, the octane number of a gasoline fraction product cannot be influenced even if the material flow is over cracked, and the production of a target product can be realized only by controlling the cracking/isomerization degree according to the product requirement, so that high-quality components in the cracking/isomerization material can be furthest reserved in the product fraction while the heavy oil material is processed to produce the high-octane number gasoline, thereby improving the content of the target components in diesel oil and tail oil products and improving the quality.

The hydrofining catalyst of step a) comprises a carrier and a hydrogenation metal loaded. Based on the weight of the catalyst, the catalyst generally comprises 10-35% of metal components in VIB group of the periodic table of elements, such as tungsten and/or molybdenum, calculated by oxide, and preferably 15-30%; group VIII metals such as nickel and/or cobalt are present in amounts of 1% to 7%, preferably 1.5% to 6%, calculated as oxides. The carrier is inorganic refractory oxide, and is generally selected from alumina, amorphous silica-alumina, silica, titanium oxide and the like. The conventional hydrocracking pretreatment catalyst can be selected from various conventional commercial catalysts, such as hydrogenation refining catalysts developed by the Fushu petrochemical research institute (FRIPP), such as 3936, 3996, FF-16, FF-26, FF-36, UDS-6 and the like; it can also be prepared according to the common knowledge in the field, if necessary. The purification catalyst should be loaded upstream of the conversion catalyst.

The grading hydrogenation conversion catalyst in the step b) is at least three hydrocracking catalysts containing molecular sieves, which are specially prepared according to the method, filled according to the difference of the types of aromatic hydrocarbons in the raw oil. And sequentially filling a heavy aromatic hydrocarbon hydrogenation conversion catalyst, a light aromatic hydrocarbon hydrogenation conversion catalyst and a monocyclic aromatic hydrocarbon retention catalyst from top to bottom according to the reactant flow direction.

The corresponding heavy aromatics hydroconversion catalyst is a hydroconversion catalyst containing a molecular sieve, and is a catalyst specially prepared according to the method. The hydrogenation conversion catalyst comprises hydrogenation active metal, a molecular sieve component and an alumina carrier. The general hydro-conversion catalyst is composed of hydrogenation active metal components such as Wo, Mo, Co, Ni and the like, a molecular sieve component, an alumina carrier and the like. The catalyst comprises WO by weight₃(or MoO)₃) 9-29 wt%, NiO (or CoO) 5-10 wt%, Y-type molecular sieve 15-45 wt% and alumina 20-50 wt%. In the heavy aromatics hydroconversion catalyst, the Y-type molecular sieve is a small-grain Y-type molecular sieve. The grain size of the small-grain Y-type molecular sieve is 400-600 nm, the infrared total acid is 0.3-0.7 mmol/g, and the proportion of the medium-strong acid is 50% (mmol/g)^-1/mmol·g^-1) The unit cell parameter is 2.435-2.440 nm; the pore volume is 0.5-0.7 cm³The proportion of the 2-8nm secondary pore volume in the total pore volume is more than 60 percent. The Y-type molecular sieve has more accessible and exposed acid centers, is beneficial to the diffusion of hydrocarbon molecules, can improve the preferential conversion capability of cyclic hydrocarbons, particularly tricyclic and higher aromatic hydrocarbons, directionally saturates and breaks aromatic rings in the tricyclic aromatic hydrocarbons, and produces gasoline components with high octane number to the maximum extent. The hydroconversion catalyst containing the small crystal grain Y-type molecular sieve is mainly used asThe catalyst can be used for selectively reacting tricyclic aromatic hydrocarbon in raw materials, and has poor selectivity on non-tricyclic two-ring aromatic hydrocarbon and non-tricyclic single-ring aromatic hydrocarbon. The Y-type molecular sieve has a certain difference with the conventional Y-type molecular sieve, the grain size of the conventional modified molecular sieve is generally 800-1200 nm, and the pore volume is 0.35-0.50 cm³The proportion of secondary pore volume to total pore volume is generally 30-50%, and the proportion of medium strong acid is 50-70% (mmol. g)^-1/mmol·g^-1). The hydroconversion catalyst may be used to prepare a satisfactory catalyst in accordance with common general knowledge in the art, as described above.

The corresponding light aromatic hydrocarbon hydrogenation conversion catalyst is a hydrogenation conversion catalyst containing a molecular sieve, and is a catalyst specially prepared according to the method. The hydrogenation conversion catalyst comprises hydrogenation active metal, a molecular sieve component and an alumina carrier. The general hydro-conversion catalyst is composed of hydrogenation active metal components such as Wo, Mo, Co, Ni and the like, a molecular sieve component, an alumina carrier and the like. The hydroconversion promoter metal specifically used in the present invention is preferably Ni, which includes WO by weight₃(or MoO)₃) 5-15 wt%, NiO (or CoO) 3-8 wt%, molecular sieve 50-60 wt% and alumina 5-30 wt%; the molecular sieve may be a Y-type molecular sieve. Further, the Y-type molecular sieve has the following properties: the particle size is 600-800 nm, the unit cell parameter is 2.438-2.442 nm, the infrared total acid is 0.6-0.8 mmol/g, and the proportion of the medium strong acid is 80% (mmol/g)^-1/mmol·g^-1) Wherein the proportion of the 2-8nm secondary pore volume in the total pore volume is more than 50%. The modified Y molecular sieve can be obtained by modifying by a conventional method in the field. The light aromatic hydrocarbon hydroconversion catalyst has the main function of performing selective reaction on bicyclic aromatic hydrocarbon in raw materials, and has poor selectivity on other aromatic hydrocarbon. The present hydroconversion catalyst is a proprietary technical catalyst that can be prepared according to the above description, following common general knowledge in the art.

The corresponding single-ring aromatic hydrocarbon retention catalyst is a hydroconversion catalyst containing a molecular sieve, and the hydroconversion catalyst comprises hydrogenation active metal, a molecular sieve component and an alumina carrier. The general hydroconversion catalyst is prepared from hydrogenation active metal components such as Wo, Mo, Co, Ni and the like, and moleculesA sieve component, an alumina carrier and the like. The hydroconversion catalyst metal composition specific for the present invention is preferably Mo-Co, which includes MoO by weight₃5-25 wt%, CoO 3-8 wt%, molecular sieve 20-40 wt% and alumina 30-50 wt%, wherein the molecular sieve can be a Y-type molecular sieve. Further, the preferred Y-type molecular sieve has the following properties: the particle size is 500-700 nm, the unit cell parameter is 2.438-2.440 nm, the infrared total acid is 0.6-0.7 mmol/g, and the proportion of the medium-strong acid is 70% (mmol/g)^-1/mmol·g^-1) The proportion of the secondary pore volume of 2-8nm to the total pore volume is5155 percent. The catalyst is characterized in that the preparation process of the molecular sieve adopts a modified Y-type molecular sieve which has moderate acid strength and more non-framework aluminum and is beneficial to retaining monocyclic aromatic hydrocarbon. The main function of the catalyst is to retain monocyclic aromatic hydrocarbons in the upper transfer stream and to selectively react other components than monocyclic aromatic hydrocarbons. The present hydroconversion catalysts may be prepared in accordance with common general knowledge in the art, as described above.

The three catalysts need to consider the excessive cracking performance in the grading process, namely, the heavy aromatic hydrocarbon hydroconversion catalyst at the top contacts the refined oil containing nitrogen and mainly reacts on the polycyclic aromatic hydrocarbon, so the cracking performance does not need to be excessively high; the light aromatic hydrocarbon hydrogenation conversion catalyst filled at the lower part of the catalyst has the task of producing high octane gasoline, and simultaneously, the reaction of bicyclic aromatic hydrocarbon is needed, and the cracking activity of the catalyst is higher than that of the heavy aromatic hydrocarbon hydrogenation conversion catalyst; the function of the single-ring aromatic hydrocarbon retaining catalyst at the lowest part is to retain the single-ring aromatic hydrocarbon and simultaneously prevent low-octane components from entering the gasoline fraction, so that the cracking activity of the catalyst is not too high and is close to or slightly lower than that of a heavy aromatic hydrocarbon hydro-conversion catalyst.

The hydrocracking catalyst in the step d) is a conventional catalyst in the technical field, and the hydrocracking catalyst with double functions of hydrogenation and isomerization is used for the invention. The hydrocracking catalyst generally comprises amorphous silica-alumina, a modified beta molecular sieve, a refractory porous oxide and oxides of metals in families VIB and VIII, wherein the metals in the families VIB and VIII are W and/or Mo, and the metals in the families VIII are Ni and/or Co. Based on the weight ratio of the catalyst, the content of each component in the catalyst is oneThe method comprises the following steps: 29-50 w% of amorphous silica-alumina, 1-9 wt% of modified beta molecular sieve, 15-35 wt% of VIB group metal calculated by oxide, 3-9 wt% of VIII group metal calculated by oxide and 0-45 wt% of porous refractory oxide; in which SiO of molecular sieve b is modified₂/Al₂O₃The weight ratio is 50-90, the average size of crystal grains is 0.1-0.5 micron, and the infrared acidity is 0.1-0.4 mmol/g. The hydrocracking catalyst can be selected from various existing commercial catalysts, such as FC-14, FC-20 and other catalysts developed by FRIPP. It is also possible to prepare specific hydro-upgrading iso-pour point depressants according to the general knowledge in the art, if necessary, for example a satisfactory hydrocracking catalyst can be prepared with reference to the disclosure in CN 1712498A.

In the hydrogen separation in the step c), namely the process of cold high-temperature separation of liquid phase and gas phase, the converted gasoline can be extracted from the bottom of the final naphtha fractionating tower; the gas-liquid separation, stripping, fractionation processes described in step c) and step d) are well known to those skilled in the art. The gas-liquid separation is a separation process of products in the hydro-conversion/cracking process, generally mainly comprises a high-low pressure separator, a circulating hydrogen system and the like, and the separation and extraction process of the converted gasoline in the invention basically needs a thermal high-split flow; the fractionation process is a process for further refining a liquid-phase product of gas-liquid separation, and generally mainly comprises a stripping tower, a fractionating tower, a side-line tower and the like.

The converted gasoline in the step c) is a gasoline component obtained in the hydro-conversion process, generally the sulfur content is less than 10 mug/g, and the research octane number is more than 85.

The heavy naphtha, the low-freezing point diesel oil and the unconverted oil in the step d) are products obtained by processing non-aromatic components, so that the aromatic hydrocarbon content is extremely low, and the heavy naphtha is preferably used as a raw material for preparing ethylene by steam cracking; owing to the isomerization of hydrocracking catalyst, the diesel oil and unconverted oil have low solidifying point and may be used as the base oil material for low solidifying point diesel oil and lubricating oil.

Compared with the prior art, the method for producing the high-quality gasoline has the following advantages:

1. proper heavy oil raw materials are selected, and after selective saturation and ring opening and chain scission of hydrogenation conversion of a special catalyst, polycyclic aromatic hydrocarbon in the raw materials is converted into high-quality gasoline components, and the obtained gasoline components have the characteristics of low sulfur content and high octane number and can be subjected to blending production. After separation, the diesel oil obtained by subsequent reaction has the characteristics of low sulfur content and low condensation point, and the tail oil component has the characteristics of low sulfur content and low condensation point, is rich in high-quality lubricating oil base oil raw material components, and can produce lubricating oil base oil under the condition of no pour point depression; under the condition of the method, the properties of other components obtained also have advantages, and the components can be directly used as ethylene cracking raw materials or fuel oil products for production. The invention can convert heavy distillate oil into high-quality gasoline as a target product to the maximum extent, and simultaneously produces high-quality low-freezing point diesel oil and lubricating oil base oil as byproducts, thereby finding an economical and feasible line for processing inferior raw materials and producing gasoline and low-freezing point oil and having great practical advantages.

2. The method of the invention carries out grading sectional processing on the heavy oil hydroconversion/cracking/isomerization in the process flow, and obtains ideal comprehensive processing effect on the basis of improving the quality of the raw materials of gasoline products, low-freezing diesel oil and base oil. In the process flow, the method does not need to greatly transform the device, can realize the purpose of high-quality production through the combination of the catalyst, the adjustment of physical properties and the coupling of units, has the advantages of equipment saving, low operation cost and the like, reduces the investment, and has wide application prospect.

3. The method of the invention makes certain limitation on the process condition, has rigid requirements on the reaction depth of a refining section and a conversion section, and aims to convert polycyclic aromatic hydrocarbon in heavy raw oil into monocyclic aromatic hydrocarbon as much as possible, retain the monocyclic aromatic hydrocarbon in gasoline fraction, and simultaneously play a role of avoiding over-cracking of low-octane number fraction, thereby causing the phenomenon of gasoline quality reduction.

3. According to the method of the invention, a new hydroconversion catalyst is developed, which is a great embodiment of technical progress, the production way of high-quality gasoline can be widened, in addition, the newly developed hydroconversion catalyst is purposefully graded, researched and filled according to the content of aromatic hydrocarbon in the raw material, the degree of main reaction under the conversion working condition of the method can be realized, in the past, in the production process, for the hydrogenation process of the wax oil raw material, if light fractions are produced, only heavy naphtha raw material with high aromatic hydrocarbon potential can be provided for a catalytic reforming device, but high-quality gasoline cannot be directly produced, but the method can directly convert the wax oil raw material into gasoline products with market demands, has great competitive advantages technically, and simultaneously, the produced low-freezing products can also be used as low-freezing diesel oil and lubricating oil base oil raw materials, thereby providing more production flexibility for enterprises, bringing intuitive economic benefits.

Drawings

FIG. 1 is a schematic flow diagram of the process of the present invention.

Detailed Description

The combined process of the present invention will be described in detail with reference to the accompanying drawings. Only the main description of the process flow is given in fig. 1, and some necessary equipment and vessels are also omitted from the schematic.

As shown in FIG. 1, the process flow for producing gasoline of the present invention is as follows: mixing a heavy raw material 1 and hydrogen 2, and then entering a hydrofining reaction zone to contact and react with a hydrofining catalyst 3; the reaction effluent 4 enters a hydro-conversion reaction zone to be in contact reaction with graded hydro-

conversion catalysts

5, 6 and 7; after the reaction effluent 8 enters a separation unit 9, a gas phase stream 10 is discharged from the upper part and enters a treatment area 11 containing hydrogen separation, stripping, fractionation and other units, finally, converted gasoline 13 is discharged from the bottom, and a light component 12 is discharged from the top; liquid phase material flow 14 is discharged from the bottom of the separation unit 9, mixed with hydrogen 15 and then enters a hydrocracking/isomerization reaction zone to contact and react with a hydrocracking catalyst 16, effluent 17 enters a unit containing gas-liquid separation, stripping, fractionation and the like for treatment 18, high-quality naphtha 19 is obtained at the upper part, low-freezing diesel oil 20 is obtained at the middle part, and low-freezing tail oil 21 is obtained at the bottom. The catalyst 3 is a hydrofining catalyst, the

catalysts

5, 6 and 7 are heavy aromatics, light aromatics and monocyclic aromatics respectively and retain a hydroconversion catalyst, and the catalyst 16 is a hydrocracking catalyst with an isomerization function.

The combined process of the present invention is further illustrated by the following specific examples.

Example 1

The combined process flow shown in figure 1 is adopted, straight-run wax oil is selected as a conversion/cracking/isomerization raw material to carry out hydrogenation to produce gasoline, and certain refining (nitrogen content 100 ppm) and conversion depth (gasoline yield 30%) are controlled. The catalysts used in the examples are commercial catalyst FF-36 hydrotreating catalyst, special hydroconversion catalyst A, B, C single ring aromatics retention hydroconversion catalyst, and commercial catalyst FC-14 hydrocracking catalyst.

The properties of catalyst A, B and C are shown in Table 1, the properties of the feed oil are shown in Table 2, and the operating conditions are shown in Table 3.

Example 2

The combined process flow shown in figure 1 is adopted, straight-run wax oil is selected as a conversion/cracking/isomerization raw material to carry out hydrogenation to produce gasoline, and certain refining (nitrogen content of 200 ppm) and conversion depth (gasoline yield of 30%) are controlled. The catalysts used in the examples are commercial catalyst FF-36 hydrotreating catalyst, special hydroconversion catalyst A, B, C single ring aromatics retention hydroconversion catalyst, and commercial catalyst FC-14 hydrocracking catalyst.

Example 3

The combined process flow shown in figure 1 is adopted, straight-run wax oil is selected as a conversion/cracking/isomerization raw material to carry out hydrogenation to produce gasoline, and certain refining (nitrogen content of 200 ppm) and conversion depth (gasoline yield of 20%) are controlled. The catalysts used in the examples are commercial catalyst FF-36 hydrotreating catalyst, special hydroconversion catalyst A, B, C single ring aromatics retention hydroconversion catalyst, and commercial catalyst FC-14 hydrocracking catalyst.

Comparative example 1

Comparative example 1 is a hydrocracking process for processing straight-run wax oil, the naphtha yield is controlled to 20% according to the conventional hydrofining depth, the comparative product is heavy naphtha, and the catalysts used in the comparative example are a commercial catalyst FF-36 hydrotreating catalyst and an FC-14 hydrocracking catalyst.

The properties of the feed oil are shown in Table 2, and the operating conditions are shown in Table 3.

Comparative example 2

Comparative example 1 is a hydrocracking process for processing straight-run wax oil, the naphtha yield was controlled to 30% according to the conventional hydrofining depth, the comparative product was heavy naphtha, and the catalysts used in the comparative example were commercial catalysts FF-36 hydrotreating catalyst and FC-14 hydrocracking catalyst.

TABLE 1 tailoring the principal physicochemical properties of the conversion catalyst

TABLE 2 raw oil Properties Table

TABLE 3 reaction conditions

TABLE 4 Main Properties

It can be seen from the above examples that the use of the present invention for treating heavy oil feedstocks, compared to the comparative examples, eliminates the catalytic reforming process, directly produces high octane, low sulfur gasoline products, and produces low sulfur, low nitrogen, low freezing point liquid products, and is technically advantageous.

Claims

1. A method for producing gasoline and low freezing point oil by a catalyst grading technology comprises the following steps:

a) under the condition of hydrofining, the heavy oil raw material and hydrogen are mixed and then pass through a reaction zone containing a hydrofining catalyst bed layer to carry out limited hydrofining reaction; the limiting hydrofining means controlling the nitrogen content of the refined oil obtained in the step a) to be 50-250 mu g.g^-1；

b) Carrying out a limited hydro-conversion reaction on the reaction effluent obtained in the step a) through a reaction zone containing a graded wax oil hydro-conversion catalyst bed layer under the hydro-conversion process condition, and separating the reaction effluent in a flash tank to obtain a gas phase containing a gasoline component and a liquid phase with a distillation range larger than that of gasoline fraction; the limiting hydroconversion reaction is to control the yield of gasoline fractions in the total product to be 10-40 wt%;

d) carrying out hydrocracking/isomerization reaction on the liquid phase obtained in the step b) through a reaction zone containing a wax oil hydrocracking catalyst bed under the hydrocracking process condition, and carrying out gas-liquid separation and fractionation on the obtained reaction effluent to obtain heavy naphtha, low-freezing diesel oil and unconverted oil;

the total aromatic hydrocarbon content in the heavy oil raw material is more than 40wt%, and the nitrogen content is 800 mu g.g^-1The above;

the graded wax oil hydro-conversion catalyst sequentially comprises a heavy aromatic hydro-conversion catalyst, a light aromatic hydro-conversion catalyst and a monocyclic aromatic retention catalyst according to the direction of a reactant flow;

the heavy aromatics hydroconversion catalyst comprises hydrogenation active metal, a Y-type molecular sieve and an alumina carrier; the particle size of the Y-shaped molecular sieve400-600 nm, 0.3-0.7 mmol/g of total infrared acid, over 50% of medium-strong acid and 2.435-2.440 nm of unit cell parameter; the pore volume is 0.5-0.7 cm³The proportion of the 2-8nm secondary pore volume in the total pore volume is more than 60%;

the light aromatic hydrocarbon hydrogenation conversion catalyst comprises hydrogenation active metal, a Y-type molecular sieve and an alumina carrier; the unit cell parameter of the Y-type molecular sieve is 2.438-2.442 nm, the infrared total acid is 0.6-0.8 mmol/g, the proportion of the medium-strong acid is more than 80%, wherein the proportion of the secondary pore volume of 2-8nm in the total pore volume is more than 50%;

the monocyclic aromatic hydrocarbon retention catalyst comprises hydrogenation active metal, a Y-type molecular sieve and an alumina carrier; the particle size of the Y-type molecular sieve is 500-700 nm, the unit cell parameter is 2.438-2.440 nm, the infrared total acid is 0.6-0.7 mmol/g, the proportion of the medium strong acid is more than 70%, and the proportion of the secondary pore volume of 2-8nm in the total pore volume is 51-55%.

2. The process of claim 1 wherein said heavy oil feedstock has a total aromatics content of greater than 45 wt.% and a nitrogen content of 1000 μ g-g^-1The above.

3. The process according to claim 2, wherein the heavy oil feedstock has an end point of 450 to 580 ℃ and a density of 0.92g/cm³The above.

4. The method according to claim 2 or 3, wherein the heavy raw oil is one or more selected from vacuum wax oil, deasphalted oil or coker wax oil.

5. The process of claim 1, wherein the hydrofinishing conditions of step a) are: the reaction pressure is 6.0-13.0 MPa, the volume ratio of hydrogen to oil is 200: 1-3000: 1, and the volume airspeed is 0.1-5.0 h^-1The reaction temperature is 260-435 ℃.

6. The method of claim 1, wherein the restriction of step a) isHydrofining means controlling the nitrogen content of the refined oil obtained in step a) to be 100-200 mug g^-1。

7. The method according to claim 6, wherein the content of tricyclic and higher aromatic components in the aromatic hydrocarbon component in the reaction effluent obtained in step a) is 1 to 20 wt%.

8. The process of claim 1, wherein the flash separation conditions of step b) are: the pressure is 6.0-13.0 MPa, and the temperature is 150-300 ℃.

9. The process of claim 1, wherein the hydroconversion process conditions in step b) are: the reaction pressure is 6.0-13.0 MPa, the volume ratio of hydrogen to oil is 300: 1-1200: 1, and the volume airspeed is 0.1-5.0 h^-1The reaction temperature is 280-455 ℃.

10. The process of claim 1, wherein the hydrocracking process conditions of step d) are: the reaction pressure is 6.0-13.0 MPa, the volume ratio of hydrogen to oil is 300: 1-1200: 1, and the volume airspeed is 0.1-5.0 h^-1The reaction temperature is 280-455 ℃.

11. The process of claim 1 wherein the hydrofinishing catalyst of step a) comprises a support and a supported hydrogenation metal comprising a group VIB metal and/or a group VIII metal, the support being an inorganic refractory oxide; based on the weight of the catalyst, the content of the VIB group metal component is 10-35% in terms of oxide, and the content of the VIII group metal such as nickel and/or cobalt is 1-7% in terms of oxide.

12. The process of claim 1 wherein said heavy aromatics hydroconversion catalyst comprises WO, by weight₃Or MoO₃9-29 wt%, NiO or CoO 5-10 wt%, Y-type molecular sieve 15-45 wt% and alumina 20-50 wt%.

13. The process of claim 1 wherein said light aromatic hydroconversion catalyst comprises WO₃Or MoO₃5-15 wt%, NiO or CoO 3-8 wt%, Y-type molecular sieve 50-60 wt% and alumina 5-30 wt%.

14. The method of claim 1, wherein the single ring aromatics retention catalyst comprises MoO by weight₃5-25 wt%, CoO 3-8 wt%, Y-type molecular sieve 20-40 wt% and alumina 30-50 wt%.

15. The process of claim 1 wherein the hydrocracking catalyst of step d) comprises amorphous silica alumina, modified beta molecular sieves, refractory porous oxides, group VIB and group VIII metal oxides; based on the weight ratio of the catalyst, the content of each component in the catalyst is as follows: 29-50 w% of amorphous silica-alumina, 1-9 wt% of modified beta molecular sieve, 15-35 wt% of VIB group metal in terms of oxide, 3-9 wt% of VIII group metal in terms of oxide and 0-45 wt% of porous refractory oxide; in which SiO of beta molecular sieve is modified₂/Al₂O₃The weight ratio is 50-90, the average size of crystal grains is 0.1-0.5 micron, and the infrared acidity is 0.1-0.4 mmol/g.

16. The process according to claim 3, wherein the heavy oil feedstock has an end point of 480 to 570 ℃ and a density of g/cm³The above.

17. The method according to claim 7, wherein the content of tricyclic and higher aromatic components in the aromatic hydrocarbon component in the reaction effluent obtained in step a) is 2 to 15 wt%.